1. Field of the Invention
The present invention relates to the field of rechargeable battery systems such as may be used in battery powered vehicles and the like.
2. Prior Art
Rechargeable battery packs of substantial size are now commonly used for various applications, such as by way of example, for powering battery powered vehicles. Such battery packs generally consist of a plurality of batteries connected in series to provide battery current at a relatively high voltage. Such a battery bank is shown schematically in FIG. 1, wherein each battery cell 20 has a pair of terminals 22 and 24, the battery bank shown being comprised of a battery bank of 16 battery cells wide by 6 battery cells deep, for a total of 64 battery cells.
An overall prior art system incorporating a battery pack as shown in FIG. 1 may be seen in FIG. 2. A battery management system is typically coupled to an LCD (liquid crystal display) for displaying information regarding the battery pack condition and state of charge. The battery management system is powered from a 115 VAC input when the system is plugged in, so to speak, and otherwise is powered from the DC power of the battery pack itself. The battery management system monitors and controls a battery charger also powered from the 115 VAC input through a communication link, with the main high voltage charger charging all of the battery cells in the battery pack. The communication link and control is coupled to each battery cell so that the condition (state of charge and general health) of each battery cell in the battery pack may be monitored to detect which battery cells most seriously need charging and whether any battery cells in the battery pack will not satisfactorily charge or tend to overheat. Battery cell balancing is also included in this prior art.
The prior art system of FIGS. 1 and 2 works well when all battery cells are in good condition and the terminal voltage of the batteries in the battery pack is well balanced. However, if a single battery cell in the battery pack fails, the entire battery pack must be disassembled, the bad battery cell replaced and the battery pack rebalanced before the battery system may be used again. Consequently, in the prior art whenever a bad battery cell is encountered, the entire battery pack must be serviced before it can be recharged, making the failure of a single battery cell a catastrophic failure for the battery system.